The present invention relates generally to switch-mode power converters. More particularly, the present invention relates to power supplies using synchronous rectifier circuitry in place of a diode bridge. Even more particularly, the present invention relates to control circuitry for driving synchronous rectifiers according to input voltage phase.
Various switch-mode power converters as conventionally known in the art include bridge rectifiers to convert an alternating-current (AC) input voltage into a rectified direct-current (DC) voltage. However, losses on such a bridge rectifier may be significant. The voltage drop for typical bridge diodes may range from about 0.7 volts to about 1.0 volts. Hence, the diode voltage drop may be as much as 2 volts as in a bridge rectifier there are two diodes conducting for every half cycle of the AC input signal.